HP Forum Archive 15

[ Return to Index | Top of Index ]

Re: HP-29C: another faulty calculator through eBay... Message #1 Posted by David Smith on 22 Feb 2006, 9:59 a.m. Dancing and flashing digits is NOT a typical ACT symptom. I've seen many 29C's with this problem. Most likely cause is a bad filter capacitor in the DC-DC converter inside the calculator.

Re: HP-29C: another faulty calculator through eBay... Message #2 Posted by Andreas Terzis on 22 Feb 2006, 4:38 p.m., in response to message #1 by David Smith Does anyone have any info about what Bram said below (harming the calc when using regular AA batteries)?

Re: HP-29C: another faulty calculator through eBay... Message #3 Posted by Bram on 23 Feb 2006, 4:01 a.m., in response to message #2 by Andreas Terzis It may have been a message in this forum; I cannot remember quite right. On the other hand, here someone shares my experience that it didn't harm. As long as I haven't read a proof that the voltage difference between NiCds and alkalines (0.6 V) can or cannot harm, I don't take the risk (anymore). It looks like you shouldn't worry about having applied alkalines though.

Re: HP-29C: another faulty calculator through eBay... Message #4 Posted by Andreas Terzis on 23 Feb 2006, 4:51 a.m., in response to message #3 by Bram Bram, I didn't understand. Did the alkalines have to be connected on one end as well? I am not sure how that solution worked. Can you please clarify? Thanks, Andreas

Re: HP-29C: another faulty calculator through eBay... Message #5 Posted by Vassilis Prevelakis on 23 Feb 2006, 7:06 a.m., in response to message #4 by Andreas Terzis since we are talking about series 2x calculators, here is a picture of the battery pack of my HP-21: you can see the two alcaline batteries. They are linked on the rear by the existing springs in the HP-21 pack. I had to remove the plastic strip on the top of the pack to allow easy access to the batteries. **vp

Re: HP-29C: another faulty calculator through eBay... Message #6 Posted by Bram on 23 Feb 2006, 10:49 a.m., in response to message #5 by Vassilis Prevelakis Thank you, Vassilis. Clear picture. I did exactly the same thing: remove the middle bar, take out the NiCd cells (little force needed) and put 2 alkalines back in. If you use the calculator often and frequently replace the batteries it may be handy to write big pluses and minuses at all proper places in the compartment, and fix the spring with a little piece of tape with 2 sticky sides ('double fix' as it is called in NL). I have the impression that alkalines are a bit longer and often have a smaller "head". This may cause more tension to the circuit board, so I always put the pack in the calc very carefully. But, as said before, I hold on to the safe NiCds nowadays.

[ Return to Index | Top of Index ]

Go back to the main exhibit hall